Influenza A virus causes highly contagious respiratory diseases in a variety of avian and mammalian hosts, including humans and pigs. The recent emergence and pandemic classification of novel swine-origin influenza A H1N1 virus, 2009 A (H1N1) poses a significant threat to public health. There are concerns that the virus may reassort with seasonal human influenza viruses giving rise to either increased transmissibility or pathogenicity. In particular, these viruses appear to retain the potential to transmit back to swine and thus continued reassortment with swine viruses may generate more virulent viruses. Identification and implementation of effective strategies to prevent current and future outbreaks are needed. The primary means for controlling influenza virus epidemics is vaccination, with neutralizing antibody against the surface glycoprotein HA being the target of most of the currently licensed influenza virus vaccines. However, the efficacy of vaccination towards influenza virus is severely limited by rapid antigenic variations within the HA gene (antigenic drift). Ferret postinfection antisera raised against the currently circulating seasonal human A (H1N1) viruses did not react with the 2009 A (H1N1) swine-origin stains. Historically, inclusion of more than one isolate per subtype of influenza has been limited by antigenic constraints, including the amount of HA required to stimulate immunity, the total HA content tolerance, and the potential for immunodominance by one vaccine strain over the other. In order to develop a vaccine that can be broadly effective against various strains of virus, and limit the spread of novel swine-origin H1N1 influenza viruses, this proposed study will test the feasibility of a molecular breeding (DNA shuffling) approach to create novel HA genes of influenza H1N1 viruses for development of broadly protective vaccines. This approach will create the novel HA genes by combination of HA genes from swine and human- origin influenza H1N1 viruses representing five distinct phylogenetic clusters. The efficacy of the shuffled chimeric HA antigen-induced protection will be assessed using a pig challenge model. Specific aims are: 1) To create chimeric HA genes by molecular breeding (DNA shuffling) of influenza HAs from five major phylogenic clusters of influenza A H1N1 viruses;2) To evaluate the potential of using the shuffled chimeric HA antigen as a subunit vaccine in a pig challenge model. This study will generate novel HA antigens and test their ability to induce broad immune responses against swine and human-origin influenza A H1N1 viruses. Development of a vaccine in this manner will serve as a proof of principle that vaccines inducing immune response toward both human and animal viral isolates will provide broad immunity, and prevent future emergence of novel HAs from animal sources into the human population. The research team will recruit highly motivated undergraduate students to participate in the project, which provides valuable training in research methods, disease mechanisms and disease prevention (refer to attached document: Undergraduate student training). PUBLIC HEALTH RELEVANCE: Seasonal influenza virus infections are associated with 3-5 million hospitalizations and 250-500,000 deaths on an annual basis in the industrialized world. The recent emergence of the swine-origin influenza A (H1N1) virus that is genetically divergent from human seasonal influenza vaccine strain exemplifies the need for development of an effective vaccine in a short period of time. This proposed study will use molecular breeding approach by DNA shuffling and screening to generate chimeric influenza HA antigens that have the capacity to induce a broadly protective immune response against swine and human-origin influenza A H1N1 viruses. The technology established in this study can be applied to chimeric HA genes within (or between) other subtypes of influenza virus. The long term goal of our study is to develop universal vaccines that can elicit broad immunity to prevent future pandemics.